1. Field of the Invention
The present invention relates to a hoisting and lowering device, which hoists and lowers a hoisting and lowering table in parallel with a set surface for use by production facilities in various kinds of production fields, a transfer facility, a care facility in a medical welfare field, a stage facility in an art field and the like, and more specifically relates to an engagement chain type hoisting and lowering device in which an engagement chain is adopted as a driving medium for hoisting and lowering operations.
2. Brief Description of the Related Art
In the field of hoisting and lowering devices, there has been a hoisting and lowering device, which hoists and lowers articles to be hoisted and lowered such as heavy articles by use of an engagement chain, which is integrally hoisted and lowered while being engaged with each other, a socalled chuck chain (see Japanese Laid-Open Patent Publication No. Hei. 11-278 797, particularly page 1 and FIG. 1).
However, since in a hoisting and lowering device using a conventional engagement chain, an engagement chain, which hoists and lowers while supporting the entire load containing articles to be hoisted and lowered, loaded on a loading rack-shaped load supporting member, is provided on one side of the load supporting member, in a case where articles to be hoisted and lowered are loaded on the load supporting member in a biased state, a biased load is loaded on one side of the load supporting member so that a loading surface of the load supporting member is changed from a parallel state to an inclined state. Thus, various ideas for making the shape of the load supporting member to be a box shape so that articles to be hoisted and lowered do not slide down have been required. And there has been a troublesome problem in that handling loading and unloading of the articles to be hoisted onto and lowered from such a box-shaped load supporting member becomes difficult. Further, there was a problem in hoisting and lowering operations that an engagement chain, which hoists and lowers while supporting the entire load containing loaded articles to be hoisted and lowered in an engaged state is liable to buckle so that the endurance of the chain is lost and unstable hoisting and lowering operations due to rolling of the engagement chain are liable to occur.
Further, since in the hoisting and lowering device using a conventional engagement chain, a motor, which hoists and lowers an engagement chain and a vertical wall-shaped accommodating guide portion are arranged in the vicinity of a pair of sprockets, the lowering position of the load supporting member cannot be lowered due to the sizes or heights of the driving motor and the pair of accommodating guide portions. That is, there were problems in hoisting and lowering operations, because the floor of the load supporting member cannot be lowered, and a large operational burden is required for loading and unloading of articles to be hoisted onto and lowered from the load supporting member.